Earth History Final Exam Study Guide
Earth History Final Exam Study Guide GEOL 1210
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Date Created: 05/07/16
Earth History Final Exam Study Guide Origin of Earth Solar Nebula Theory (4.56 billion yrs. ago) Exploding star initiated the process of the birth of our solar system and Earth Nebulas consist of hydrogen and helium left over from the Big Bang Ex. Eagle Nebula Our galaxy, the Milky Way, spins counterclockwise and so does everything within it The planets revolve around the sun counterclockwise Earth spins on its axis counterclockwise Compositional Gradient: Heavier elements (Nickel & iron) condensed closer to the sun (the Rocky planets) Gaseous Giants: Jovian planets, composition of lighter elements because farther away from the Sun Age of Materials: Earth The Moon Meteorites (Asteroids) Early radioactivity heated the interior of the Earth as the radiation from the sun was not powerful enough for those processes, this caused the differentiation of the Earth’s layers Meteorite Evidence Chondrites (Stony): mantle 4.56 billion years ago Ultramafic composition Early Solar System composition Iron meteorites Metallic composition Cores of planetary bodies Stonyiron meteorites Mixture of rocky and metal Boundary between core & mantle Oxygen – rich rocks: Earth’s crust & Moon Collision of Earth and the Moon caused Earth’s 23.5° tilted axis At this point in time, igneous rocks formed on Earth as it cooled down from its molten form Two sets defining Earth’s layers Composition: Crust O/Si oceanic (3 – 10 km) & continental crust (40 – 60 km thick) Mantle SiO 2 /Fe Mg 2 Core Fe/Ni Oceanic crust is denser, mafic and therefore sinks lower Continental crust is lighter, felsic and therefore more buoyant Properties: Lithosphere: brittle (stress will cause it to fracture) Plasticity vs Asthenosphere: elastic & bend Elasticity changes Mesosphere: plasticlike behavior (bend and remain in that position) Outer Core: liquid Inner Core: solid Lithosphere incorporates a bit of the mantle along with the crust Bowen’s Reaction Series Crust Formation Terrane: behave as a coherent unit; geologically distinct region of the crust **Cratons: much older rock than most of the continental crust, older than 3 billion years and located in the core of the continental crust Shields: crystalline igneous rock and metamorphic composure that has been exposed since the Precambrian time and form tectonically stable parts Iceland: located on top the midocean ridge, volcanic (oceanic) hotspot shows what Earth’s early stages of development were like as the layering of Earth in the first 2 – 3 million years was molten Largely mafic, with few felsic particles Komatiite: ultramafic & extrusive and found in Iceland but is no longer being formed on Earth present day because conditions are too cold now for it. The earth’s radiogenic levels have decreased over time Or**Destroys previous **More balanced side rocks in order to form of the series, Granitegneiss complex: extraordinarily large bodies of continentcontinent next rock crystalline percentage convergent felsic material Greenstone Belts (trough, ushaped): extrusive igneous rocks (basalts, greywacke) Absolute Dating Numerical Age: Names of the periods of geological time were set without numerical value and based on the fossil occurrences Tool to place numerical value: Radioactive Decay (isotopes) Isotopes to reach a stable state from instability Emit Alpha Particles: 2 protons & 2 neutrons results in the change of element because atomic number changes higher Ex. Potassium Argon Emit Beta Particles: Neutron releases an electron Result: proton formation from break down (change of element because atomic number changes higher) Electron Capture: electron collides with nucleus and attaches to a proton formation of electron Result: element changes, but lower on periodic table, NOT higher 1 HalfLife: time for of a nuclei to decay & as the parent decreases, the daughter increases 2 HalfLife Parent Daughter 1 50% 50% 2 25% 75% 3 12.5% 87.5% **Each isotope has its own unique halflife Carbon14: 5740 year halflife (shortest halflife) Radiometric Dating: Crystals: Parent & Daughter not the same size, once formation is complete becomes a closed system Blocking Temperature: Closed System Higher than the Blocking Temperature: system opens up & allows Daughter crystals to leave, while Parent crystals remain, therefore the structure of the crystal remains Higher > Blocking Temperature resets the time to determine age of crystal Dating Material: grade of metamorphism **Understand the thermal history of rocks because of the resetting of the time Dating Techniques: Sedimentary Rocks: not datable (for the most part) Why so? Sedimentary rocks are composed of parts of sediments & minerals stuck together Several intervals of history joined together Carbon14 Dating: not for dating minerals, but parts of organisms: teeth, bones, wood N14 (stable) C14 (unstable) Solar Radiation Starts converting back to N14 Three Carbon Isotopes C12 C13 C14 James Hutton: Father & Founder of Modern Geology: claiming that Earth was perpetually formed Erosion & sedimentary processes in the present day Plutonists: Supported the theory that rocks formed from volcanic, erosion, and weathering processes (Roman god: Pluto) James Hutton; Supported Uniformitarianism Uniformitarianism: changes in the Earth’s crust during geological history have resulted from the action of continuous and uniform processes Neptunists: believed in the OPPOSITE of Plutonists; rocks formed from the crystallization of minerals in the Earth’s oceans (Roman god: Neptune) Nicholas Steno: est. the foundation for the relative dating laws along with the Danish naturalist: Robert Hooke System: a group of interconnected units that interact with outside forces to achieve a goal Ex. Biological systems are easiest to visualize: human body, ecosystems (NOT static) Systems produce feedback: Positive Feedback: goes in only one direction, so the state of the system progressively worsens; imbalance Ex. Ice Age: glaciers, reflect sunlight back into space causing little to no absorption of heat thereby further cooling the planet drastically Negative Feedback: balanced system, two directions Ex. Ecosystems A modification of the process produced by a system to help/hinder: results and effects *Systems can vary in complexity depending on number of pieces and interactions Catastrophism: sudden, violent, & shortlived terrestrial events Actualism: human observable presentday processes also existed during the geological past therefore all past geological features existed on Earth today too Deep Time: immense span of time outside the typical human scale On a much larger scale such as…periods, eras, eons because on a geological perspective centuries and millenniums are too small – blink of an eye Relative Dating: order of events Absolute Dating: exact timing numerical value (Carbon dating) RELATIVE DATING LAWS Sedimentary Rocks Only – Steno Laws Principle of Original Horizontality: sedimentary bed formed, when it lithified it was settled horizontally Law of Superposition: vertically oriented, the rocks or sediment layers at the bottom are the oldest and the progressive layers at the top are younger Law of Lateral Continuity: as the layers form, they will extend as far as they possibly can laterally (eroded after they form) Ex. Canyons, basins, valleys Stratigraphy : the study of strata (bedded sediments) naming & identifying distribution: classification based upon physical properties, chemical features, paleontology (fossils in the grains) Ex. Minerals, grains (shape & size) Three Criteria: 1 distinct upper and lower boundary 2 meet law of lateral continuity requirements 3 vertically continuous, no break in between where something else exists Metamorphic and Igneous Rocks Principle of CrossCutting Relations: the enclosed rock fragments is older than the rock that is within Ex. Lava in Sandstone, the lava is older than the sandstone Unconformities: either rock hasn’t been deposited for a long period of time in an area or deposited but eroded away records were lost or burned, for example Three Types: 1 Disconformity: parallel bedded sedimentary rocks but there’s a discontinuity between them (rising and falling sea levels) 2 Nonconformity: metamorphic and igneous rocks eroded therefore the sediments are newly deposited Wavy, not really fitting 3 Angular Unconformity: sedimentary rocks above, below and between the unconformity Paleontology: the study of ancient life and fossils (that which is dug up, remains of the past life) Mineralized, hard components to these preserved fossils Preservations of soft parts such as skin, tissue, and muscle is rare as there are not mineral parts to help keep it in shape Lagerstatten: bountiful amounts of fossils Body Fossils: hard & soft body parts preserved Trace Fossils: nonphysical evidence of the organism existing Ex. Footprints, coprolites Fossilization: rare in itself Requires oxygenpoor environment (carbon print) Rapid burial in finegrained sediment < 1% of all organisms become fossils (matter of finding these fossils – biased view of past life**) Fossil Succession: first and last appearance of the fossil, each fossil has its own unique range Index fossils: very short stratigraphic range – few million at the most (they’re known globally and easily identifiable) Stratigraphic columns: indicate rock layers in regions Lithostratigraphy: comparing similar physical features and sequences in the rock Biostratigraphy: fossils in the stratigraphic rocks Magneto stratigraphy: when igneous rocks form they take on the magnetic characteristic t which Earth has within its formation (the minerals in the rocks point north) Event Stratigraphy: evidence of instantaneous geologic events Ex. Volcanic eruptions ash patterns Fossil Record: displays a biased view of the past life Preservation: Body Parts: hard vs soft Organisms with hard parts fossilize much easier and longer than soft parts Ex. Jellyfish, snakes Marine vs. Terrestrials: rapid burial & depositional Weathering and erosion: highland vs lowland (depositional) Big vs Small Populations: temporal range Discovery: Environment: areas not easily accessible to human beings ex. Deep oceans, extraneous environments Geographic Bias: paleontologists (dominantly white in the past) and their preferred area of excavation – Europe & N. America Rock Record Bias: tectonic activity causing the older rocks to subduct and form new rocks New rock, therefore rare fossilization As long as the sample group of fossils is large enough all of the trends will be exhibited The biased view will not be significant enough to change trends in the data EVOLUTION: change over time Natural Selection: model of evolution that proceeds 1 Heredity of most features: Parents Offspring 2 Heritable variation in the population 3 Variation leads to different rates in survival and reproductive success (some variations are more beneficial than others, therefore survive longer and pass on these characteristics to their offspring) 4 Shift in frequency/mode towards successive characteristics 5 Given enough time Parent & Daughter can no longer interbreed b/c the differences are too extreme Can no longer be part of the same line Evidence for Evolution: Evolution Transformism: species change over time, but number of species remains the same since origin Separate Creation (Creationism): species originate separately and remain in the exact same form The existence of certain kinds of similarities (homologies) between species: similarities that wouldn’t exist if each species was created independently Species change through time and share a common ancestor Observe change on a small scale (House sparrows in N. America) and then gradually spread out and correlate changes on a much larger scale (ring species) Scientific Evidence: Once species has evolved into another in the past Or Each species had a separate origin and has remained fixed in that form ever since the beginning Two Evolutionary Claims: 1 That species in Darwin’s sense of “descent with modification” 2 That all species share a common ancestor (treelike history) Involved people’s perceptions of the world and the amount of scientific knowledge they possess along with religion Past faunas: a round of extinction followed by a round of creation of new species Evolution can also be created experimentally: A species: selecting a minority to breed a specific trait, over time the species takes to that trait and moves in the direction of that artificially created evolutionary change Ex. Agriculture: eggs laid by hens or milk yield of cows Give it long enough time span, and it is observed that artificial selection produces a dramatic change ALL living creatures are classified into a Linnaean hierarchy system 1 Kingdom 2 Phylum 3 Subphylum 4 Class 5 Order 6 Family 7 Genus 8 Species Basic Components of Climate System Distance from Sun Incoming Energy/ Solar Luminosity Climate Influences Global Albedo (Natural) Greenhouse Effect Insolance: exposure to sun Angle of Incidence Length of Daylight External Controls Atmospheric Transparency Variation in Solar Iridescence ~ Albedo: reflectivity of a surface Snow: high reflectivity Ocean: low reflectivity Earth’s Magnetism: ~ Inner core: solid & spinning Outer Core (liquid): 90% of the Earth’s magnetic field convection currents ~ Ironcontent minerals in igneous rocks align to the magnetic field (North Pole, for present time magnetism) ~ Curie Point: below this point minerals are trapped in their alignment Early Life Chemosynthetic Organisms: inject sulfur into the atmosphere Places today that prove how Earth’s processes occurred at the beginning of the planet’s life, also organisms living in these places can prove that Yellowstone National Park: Archaea (first organisms & THEN chemosynthetic organisms evolved on Earth) Archean Life: Stromatolites: cyanobacteria (blue – green algae) st 1 life (prokaryotes): 3.5 billion years ago Steranes: molecular fossils 2.7 billion years ago Chemicals that are part of eukaryotic cells (2.1 billion years ago) Organisms: CaCO3 (invertebrates) CaPO4 (bone) late Proterozoic Hard parts: store crucial elements & protect soft parts & anchorage structure for muscles & tissues defensive structure Archean cratons formed during collisions of island arcs and minicontinents during the period of the formation of Laurentia Baltica/Europe Cambrian 541 million years ago to 485.4 million years ago The cambrian saw most of the continents in the southern hemisphere. The supercontinent Pannotia continued to assemble in some regions but fragmented into Gondwana, Laurentia, and Baltica. Iapetus ocean mostly submerged Baltica during this time. o Climate was generally warm, wet, and mild this was the case everywhere. Cambrian “explosion” this was the sudden evolutionary burst. o Most the lifeforms today can be traced back to the Cambrian period. Black shale is seen along with other siliciclastics. Ordovician 488 to 444 million years ago Gondwanaland (S. Europe, Africa, S. America, Antarctica and Australia) o Moved towards South Pole Western and Central Europe were separate from Gondwanaland rotated 90 degrees counterclockwise from present orientation and in the southern tropics N. America collides with microcontinent, Baltica (later becomes Europe) this conversion leads to the shrinking of the Iapetus Ocean (in the middle of N. America and Baltica) o Iapetus ocean turns into mountain range Greenland, Norway, Scotland, Ireland and N.E. N. America o Caledonian Orogeny Avalonia and Baltica broke off from Gondwana and joined Laurentia Took 150 million years from late Cambrian to mid Devonian Subduction of Iapetus Ocean formed volcanoes. Plutonic intrusions (granites) now exposed by erosion in Scotland, N. England and Anglesey Greywackes deposited in deep waters of subduction trench Black shales deposited further out on deep ocean floor (abyssal plain) N. Wales and Anglesey repeatedly deposited sands and clay in deep water eventually regionally metamorphosed into quartzites and schists from high heat and pressure from ocean folding slates and gneiss were also found Plate collision caused faulting of the rocks Great Glen Fault, Moine Thrust, Highland Boundary Fault and Southern Uplands Fault Widespread shallow, warm epicontinental seas favorable for marine life o Gondwana suffered a severe Ice Age, Europe was unaffected due to its more northern position Silurian – 444 million years ago to 416 million years ago Siberia, Laurentia and Baltica converge at the equator, forming mountain ranges and new supercontinent Laurussia Long, warm greenhouse phase. Warm, shallow seas covered much of the equatorial land masses o Low continental elevations, high sea level65% of shallow seas flooded Seas were tropical to subtropical in climate high evaporite deposits found in N. Europe Much Wenlock Limestone Formation Wales and the Welsh Borderland (Early Silurian) o Home to 600 species of invertebrates (fossils) o Covered by relatively warm, shallow shelf sea o Six bedded lithofacies and two reef types o Carbonate shelf environments o 29 meters in thickness Devonian 367 to 408.5 million years ago Climate was largely warm and equable, until the catastrophic drops in the late Devonian o Those drops caused massive extinctions Laurentia during this time was slammed on 3 sides by other continental bodies, those being Siberia, Baltica, and Africa/S.America (see image) o This interaction was the initial formation of Pangea Marine chemistry went through huge changes, accompanied by explosions in plankton populations A big Devonian site for fossils is the Rhynie Chert o It was a peat bog, preserving a lot of plant life, even to the cellular level Devonian era is also known as “The Age of Fish” o Several species of sharks, lungfish, and rayfinned fish evolved here At the end of the late Devonian, there was a massive extinction caused by the glaciation of Gondwana, killing off masses of coral and entire coral reefs until the triassic, where they finally began emerging again After the Devonian, Baltica starts being called Europe as a part of Pangea Carboniferous 360 to 300 million years ago During this time period the beginnings of the Pangea formation began and Baltica was slowly changing into the continental mass known today as Europe The collision of Gondwanaland and Laurasia results in mountain building from Poland all the way through Central Europe and the Appalachian mountains Atmospheric changes included in an immediate rise of oxygen levels and significant decrease in Carbon dioxide which caused TWO Ice Ages at this time Variscan Orogeny: mountain belt formation that spanned through Portugal, Western Spain, Ireland, and parts of the UK Intrusions & volcanic activity in the UK because of these formations Permian 299 to 251 million years ago During this period of time, all of the world’s continents were joined together in the supercontinent Pangea From Carboniferous through middle Permian, primarily the Cisuralian Epoch, made up of the Rotliegend Group upper and lower: o Lower Rotliegend Group developed through volcanism, consisting mostly of tuffs and basaltic lavas o Upper Rotliegend Group sandstones and siltstones The Southern ice cap melted off during the Permian, and much of Europe was covered by the salty Zechstein Sea during the Guadalupian and Lopingian Epochs, which advanced and receded twice. o Zechstein Sea may have connected to the Paleotethys Ocean through southeastern Poland. o Occupied mostly by brachiopods and bivalves which could handle harsh hypersaline conditions. o Lithologies found from this time period include halite, anhydrite, dolostone, and shale. Collisions in the tectonic plates created volcanic activity which caused upheaval of the Alps. The close of the Permian brought about the worst extinction event ever recorded with more than 75 percent of plant and animal groups disappearing from land, and only 5 percent of oceanic species survived. TRIASSIC: 252202 mya Age of Reptiles Germany Triassic System Bunter (lower), Muschelkalk “mussel limestone” (middle) and Keuper (upper) Pangea straddles equator, shaped like Pac man Tethys Sea divides Laurasia in N and Gondwana in S Warm, dry, middle of Pangea was very arid N Pangea was more lush, more forests and tree ferns Middle Triassic > Merging on Eurasia and Siberia brought up Ural Mountains Late Triassic N America splits from Europe. A fault line splits S. Europe from Africa. Tethys seaway separated Africa, Europe and N. America. Late Triassic N. Europe thickly wooded subtropical. Hot and dry conditions worsened throughout Triassic due to volcanic activity in S. Africa. No ice caps or continental glaciation. Miocene o Extends from 235.3 Million years ago o Warmer global climates Modern patterns of atmospheric and oceanic circulation formed Caused the buildup of the Antarctic icecap o Appearance of grassland ecosystems brought about the appearance of herbivorous mammals like horses o In the oceans, early whales and dugongs flourished, only to be preyed upon by the herculean Carcharodon megalodon which could reach up to 15 meters long Paleogene Oligocene 1. Cooler/drier than Eocene 2. Epoch based on fossilbearing sediments in Belgium and N. Germany “older miocene” 3. Separation of Shetland from Faeroe platform allowed arctic cold water to flow S. 4. Paratethys Ocean occupied Central and N. Europe (low oxygen basin bottoms, reduced salinity, particular marine faunasrapid mollusk evolution) 5. Warmer climates returned late Oligocene Eocene: 3854 MYA 1. Rifting of N. Atlantic cut of N. America from Europe arctic channel 2. Mountain building continued in Scotland 3. Brief warming methane released from ocean floor sediments (FIRST 5 MILLION YEARS=WARMER THAN ANY OTHER TIME IN CENOZOIC) 1. subtropical b. Eocene fossils found from lake deposits in Messel, Germany Paleocene: 65.555.8 MYA 1. Mesonychia flesh eating mammal, ancestral to whales 2. Land masses were separate N. America was connected to Europe by Ellesmere Island and Greenland and other areas now submerged by N. Sea 3. “Age of Mammals” 4. Abundant flowering plants and conifers 5. Subtropical “greenhouse” climate, high ocean temps, absence of polar ice caps from Cretaceous asteroid impact 6. Abrupt warming at end of Paleocene from release of large volume of methane from seafloor sediments led to major (50%) deepsea extinction of foraminifera 7. Tethys Ocean separates Africa and Europe
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